Sexual Health — Primary Prevention of Sexually Transmitted Infections
A 24-year-old woman attends a sexual health clinic after being treated for chlamydia. She has several male partners, uses a levonorgestrel intrauterine system for contraception, and states that she does not intend to stop having multiple partners. Today her HIV, syphilis and hepatitis B tests are negative. She asks which single measure would best reduce her risk of acquiring further sexually transmitted infections. What is the best advice?
- A.Doxycycline 200 mg within 72 hours after each sexual exposure
- B.Nonoxynol-9 spermicide applied before each intercourse
- C.Consistent and correct use of male latex condomsCorrect
- D.Diaphragm with spermicide used with every intercourse
Explanation
Abstinence or a long-term mutually monogamous relationship with an uninfected partner is the most reliable way to avoid sexually transmitted infections, but this woman has said she will continue to have several partners. For her, consistent and correct use of male latex condoms with every act of intercourse is the most effective available measure: condoms reduce HIV transmission by roughly 80% and substantially lower the risk of gonorrhoea, chlamydia, trichomoniasis and hepatitis B. Her hormonal intrauterine system prevents pregnancy but offers no protection against infection, so dual protection should be advised explicitly. Doxycycline post-exposure prophylaxis is the most plausible alternative, but CDC recommends it for men who have sex with men and transgender women with a recent bacterial infection; the trial in cisgender women showed no benefit, so evidence is insufficient to recommend it for her. Nonoxynol-9 damages the vaginal epithelium and increases HIV acquisition with frequent use. A diaphragm does not cover the vaginal wall and has not been shown to prevent infection. Condoms protect less well against infections spread by skin contact, such as herpes and HPV, so HPV vaccination and HIV pre-exposure prophylaxis assessment should also be offered.
Why each option
- A.
- Doxycycline prophylaxis is recommended for men who have sex with men and transgender women; evidence in cisgender women showed no benefit.
- B.
- Frequent nonoxynol-9 use causes vaginal epithelial disruption and increases the risk of HIV acquisition, so it is advised against.
- C.
- Correct. For a woman continuing multiple partnerships, consistent and correct condom use is the most effective measure to reduce infection risk.
- D.
- A diaphragm covers only the cervix, leaving vaginal mucosa exposed, and has not been shown to prevent sexually transmitted infection.
Reference: CDC Sexually Transmitted Infections Treatment Guidelines 2021 — Primary Prevention Methods; CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial STI Prevention, MMWR 2024;73(RR-2); WHO Consolidated Guidelines on STI Prevention
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